[Tagging] Reviving the path discussion - the increasing importance of trails in OSM

[Tod Fitch]

> On May 22, 2020, at 5:24 AM, Ture Pålsson via Tagging <tagging at openstreetmap.org> wrote:
> 
> 
> 
>> 22 maj 2020 kl. 12:52 skrev Daniel Westergren <westis at gmail.com <mailto:westis at gmail.com>>:
>> 
>> […] Then there is width, which is only tagged on 3.5% of highway=path. I was discussing width of paths in another forum. For a forest path, would you say width is measured as the actual tread on the ground only? For a runner and MTB cyclist that would make sense, but for a hiker with a big backpack a width of 0.3 m may mean they think it's not possible to walk there.
> 
> We need loading_gauge=* tag. :-)
> 
> (https://en.wikipedia.org/wiki/Loading_gauge <https://en.wikipedia.org/wiki/Loading_gauge>)
> 

Width is, at least in my area, going to be a hard issue.

For background, I have been volunteering on trail maintenance teams in a near by designated wilderness area where the vegetation is largely chaparral (scrub) and this has shaped my opinion.

Many of our trails were originally ranch access roads (highway=track) and in some short sections here and there where things were scraped to bedrock the trails remains that wide, maybe 3m. However the overwhelming majority of the trail mileage have been overgrown to the point of being impassible on foot without constant maintenance. Our standard for maintaining a section of trail is that the tread (where your foot meets the ground) should be a minimum of 0.5m and that the width at shoulder level should be 2m. In the occasional areas where we have trees, etc., we strive for about 3m vertical clearance so that an equestrian can get through. Being a designated wilderness, no power tools or wheeled vehicles are allowed so access is by hiking and work is performed with hand tools.

If you look to motor vehicle roads, width is of the traveled way, not of the right of way nor of the way cleared of vegetation (i.e. side drainage or shoulders, etc.). From that point of view, a trail width should likely be the tread width. But as noted by Daniel, a hiker with a big pack might be more interested in the width at pack/shoulder level (“loading gauge”).

The issues in mapping trail width in my area include:
Chaparral is fast growing. So that 0.5m/2m width trail we fixed today will shrink each rainy season and without maintenance is likely to become impassible in maybe 5 years time.
Trail maintenance teams are lucky to be able to clean up 2km of trail in a session. So it takes multiple sessions to keep a typical trail maintained and for any given trail those are sessions occur over a number of years (we target areas where things are worst).
The result is that trail width is highly variable both over the length of a trail and over time. If mapped in high detail, the width you map this hiking season will be wrong next year. Heck, it might even be wrong next month depending on what month of the year your did your survey.

For what it is worth, I don’t usually tag the width of the trails. Mostly for the above reasons: To do it properly I’d have to be taking very detailed field notes and have to re-survey each trail at least once a year. And even if I did that, when I look at the typical data consumer I see that they usually have stale OSM data so any attempt to keep OSM up to the day correct on field conditions wouldn’t be very useful anyway.


Cheers!
Tod


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